Total Lack of Service and Incorrect Billing

I have been a loyal Vodacom customer for many years. I was offered an upgrade to my contract in May/June by Elite Mobile. They sent me a new Samsung Galaxy A7 cell phone, however I did not want this phone so I organised with vodacom to have it sent back via their couriers - RAM Couriers. RAM collected the handset from me on 2 August 2017. Since then I have been constantly calling Vodacom customer care and retentions to inform them that the phone has been returned and that they must cancel the upgrade and reimburse me for the 2 - 3 months that they had incorrectly debited me for the monthly instalments on the handset. I was assured that this would be done in August already. After logging numerous queries, I decided to visit Vodaworld in Midrand to check my account and they reassured me that the billing had been corrected and that 2 refunds were due to me at the end of September. Yesterday my debit order went off against my account and instead of receiving a credit on my account, as promised, Vodacom debited R 7 036.09 was debited from my account erroneously for the handset that was returned but Vodacom failed to credit back to my Vodacom account. I have called the accounts department yesterday and spoken to Sifiso Vilakazi and he has promised that the handset will be credited to my account and that a refund will be paid directly into my bank account. I would like a the accounts department to call me and confirm that my account will be rectified and the money refunded back into my bank account ASAP! I am still waiting for assistance after 10 days!!!!! nobody calls me back!!